There is an enormous amount of literature relating to oral dosage forms, including literature relating to the use of swellable polymers therein and the relationship between dosage form size and gastric retention. It is believed, however, that the field has failed to provide an oral dosage form that enables controlled release, prolonged gastric retention, and assurance that the drug is presented to the gastric mucosa as a solution rather than as the more irritating solid state. A description of representative art involving oral dosage forms using swellable polymers follows.
U.S. Pat. No. 3,435,110 describes pharmaceutical tablets composed of a mixture of uncrosslinked or crosslinked collagen fibrils and drug. In the uncrosslinked version, upon ingestion the collagen fibrils swell, rupture the tablet, and form a gel-like diffusion matrix from which drug is released slowly. In the crosslinked version, the fibrils do not swell upon ingestion but instead are enzymatically digested and apparently release drug by an erosion rather than diffusion mechanism.
Choulis, N. H., et al., Pharmazie (1976) 31:466-470, describe the formulation of tablets containing hydrophilic gums such as carbomer. Upon ingestion, the surface of the gum swells to form a zone that acts as a barrier to penetration of gastric fluid into the tablet interior. Release of drug from the tablet is said to be by erosion of the gum rather than by diffusion or some other mechanism.